The present invention relates to valve mechanisms, and more particularly to valve mechanisms for controlling liquid and/or gaseous flows as well as liquid and/or gaseous pressures with a motor controller including a diaphragm and a force transfer control rod to actuate the valve element.
Prior art diaphragm valves typically possess seven desirable features. First, a powerful electrical, pneumatic or hydraulic valve actuator is not required. Flow rates may be controlled by one or two small, low torque, inexpensive pilot valves such as manual cocks, solenoid valves, float valves, bi-metal valves, metal expansion valves, vapor expansion valves and/or other similar arrangements.
Second, because travel of the valve element in a diaphragm valve is almost frictionless, hysteresis is negligible. Therefore, the flow rate through a diaphragm valve can be controlled with high precision without the need for an expensive valve positioner, as is required with butterfly valves, or eccentric disk valves.
Third, tight shut-off can be achieved more economically with a diaphragm valve than is possible with valves in which the moving valve element rotates, as in butterfly valves, ball valves and plug valves.
Fourth, the controlling pilot valve can be located remotely from the main diaphragm valve. This feature is particularly beneficial for very large, manually operated valves.
Fifth, closing and opening valve speeds can be adjusted independently.
Sixth, proportional control (which is accomplished by gradually decreasing the valve travel speed as the flow rate approaches the set-point) can be achieved by varying the on-time of pulsing solenoid pilot valves.
Seventh, valve packing is eliminated with diaphragm valves.
In contrast to the foregoing desirable features, prior art diaphragm valves exhibit three undesirable features.
First, prior art diaphragm valves produce a high pressure drop compared to ball valves, gate valves and butterfly valves.
Second, prior art diaphragm valves are suitable for controlling the flow of liquids. They cannot, however, be used to control gases.
Third, prior art diaphragm valves have flow curves which produce imprecise control at very low flows.
It is, therefore, one primary aspect of the present invention to provide a new and novel diaphragm valve.
It is another aspect of the present invention to provide a new and novel diaphragm valve assembly, as above, whereby the aforesaid undesirable features are eliminated.
It is a further aspect of the present invention to provide a new and novel diaphragm valve assembly, as above, whereby the aforesaid desirable features are retained.
These and other aspects of the invention, as well as the advantages thereof over existing and prior art forms, which will be apparent in view of the following detailed specification, are accomplished by means hereinafter described and claimed.
By way of a general introductory description, a valve assembly embodying the concepts of the present invention may utilize a valve housing having an inlet port. A valve seat is disposed in the valve housing to present an outlet port that is aligned substantially axially with the inlet port. As such, an axial flow path traverses the valve. An untethered valve element, or valve disc, is positioned for pivotal movement with respect to the valve seat and to be disposed within the axial flow path generally intermediate the inlet port and the outlet port to control fluid flow therebetween. A control mechanism for the improved diaphragm valve includes a motor to reciprocate a force transfer, or control, rod that is disposed angularly relative to the axial flow path. The control rod engages the valve disc to transfer forces from the motor to the valve disc in order to effect pivotal movement of the valve disc and thereby control the effective cross section of the axial flow path.